1. Field of the Invention
The present invention relates to monitoring CO.sub.2 during endotracheal and esophageal intubations.
2. Description of the Prior Art
The physical proximity of the esophageal opening to the tracheal opening makes accidental esophageal, instead of tracheal, intubation an unfortunately common occurrence. If the esophageal intubation goes undetected the patient may be deprived of oxygen, possibly leading to morbidity or mortality. Moreover, tracheal intubation can occur accidentally in procedures where esophageal intubation was intended.
A recent study of 624 closed malpractice claims found esophageal intubation to be the most frequent specific critical incident during endotracheal intubation involving anesthesiology: 41 cases of esophageal intubation, 8 causing brain damage and 31 ending in death [Cheney, Butterworths, Boston, 1988, Gravenstein and Holzer (Eds.)] A study by Keenan and Boyan of 27 cardiac arrests due to anesthesia showed 4 incidences of unrecognized esophageal intubation [Journal of American Medical Association, Vol. 253, No. 16, pp. 2373-2377 (1985)]. Cooper et al found 18 cases of esophageal intubation out of 507 "critical incidents" and 3 out of 70 anesthesia cases with "substantive negative outcome" [Anesthesiology, Vol. 60, pp. 34-42 (1984)]. In a study of emergency intubation in the field by paramedical personnel, Stewart et al noted 14 cases of esophageal intubation out of 74 reported complications [Chest, Vol. 85:3, pp. 341-5 ( 1984)].
Many prior art attempts to detect either endotracheal or esophageal intubation where the other procedure was intended are based on the fact that the stomach liberates practically no carbon dioxide whereas the lungs liberate prodigious amounts of CO.sub.2 (200 mL/min for an adult).
These previous attempts can be summarized as follows: